Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2011
Publication Date: 12/15/2011
Publication URL: http://handle.nal.usda.gov/10113/56294
Citation: Kich, J.D., Coldebella, A., Mores, N., Nogueira, M.G., Cardoso, M., Fratamico, P.M., Call, J.E., Cray, P.J., Luchansky, J.B. 2011. Prevalence, distribution, and molecular characterization of Salmonella recovered from swine finishing herds and a slaughter facility in Santa Catarina, Brazil. International Journal of Food Microbiology. 151(3):307-313. Interpretive Summary: Swine carry bacterial pathogens known as Salmonella in their gastrointestinal tract, and contaminated pork and pork products can be vehicles of Salmonella infections in humans. The objective of this investigation was to determine the distribution and types of Salmonella in 12 swine finishing herds and a slaughter facility in Santa Catarina, Brazil. A total of 1,258 samples, consisting of environmental, feed, carcass, lymph node, and fecal material were collected, and 487 samples were positive for Salmonella. Analyses of the Salmonella strains recovered from the samples showed that they belonged to predominantly to a few Salmonella types, and many strains were resistant to various antibiotics used during swine production. Furthermore, using a molecular fingerprinting technique followed by analysis of the relationship between different sources of Salmonella, there was a correlation between various fingerprint types from strains recovered from different sources and swine carcass contamination. This study demonstrated the relationship of Salmonella types originating from various steps of a vertical swine production system to carcass contamination. This information can be used to design intervention strategies to prevent contaminated pork products from reaching the consumer.
Technical Abstract: Swine are a reservoir for Salmonella spp., and pork and pork products are vehicles of Salmonella infections. The objective of this investigation was to determine the distribution and types of Salmonella in 12 swine finishing herds and a slaughter facility in Santa Catarina, Brazil. A total of 1,258 samples, consisting of environmental, feed, carcass, lymph node, and fecal material were collected and pre-enriched in buffered peptone water. Each sample was then enriched in both Tetrathionate and Rappaport-Vassiliadis broths. Following enrichment, a portion from each broth was plated onto Brilliant-Green and XLT4 selective agars. As appropriate, one to four isolates were selected and biochemically confirmed and serotyped. From 487 positive samples, 1,255 isolates were recovered and confirmed to be Salmonella. The distribution of positive samples was as follows: finishing pen floors 26% (16/61); feed 29% (42/143); feces 44% (52/119); pooled feces 59% (35/59); slaughter holding pens 90% (36/40); lymph nodes 46% (220/478); pre-chilled carcass surfaces 24% (24/98); and post-chilled carcass surfaces 24% (62/260). The most prevalent serovars were Typhimurium, Panama, Senftenberg, Derby, and Mbandaka. By pulsed-field gel electrophoresis, 1,071 isolates were subtyped using XbaI, and duplicate isolates were removed. From the remaining 747 isolates, 163 macrorestriction profiles (pulsotypes) were identified. Six pulsotypes were considered very frequent, occurring in 33 isolates or more. Multiple correspondence analyses (MCA) were used to analyze the relationship between different sources of Salmonella. The MCA showed correlations between pulsotypes from shedding pigs (feces), herd environment (pen floors) and subiliac and prescapular lymph nodes and between lairage and carcass surface samples before and after chilling. All sources of Salmonella investigated contributed to the carrier state; however, pre-slaughter contamination at lairage was the variable most strongly associated with carcass contamination. A total of 59 different antimicrobial resistance profiles were observed in 572 Salmonella isolates. From these isolates, 17% (97/572) were susceptible to all 15 antibiotics tested, 83% (475/572) were resistant to at least one antibiotic, and 43% (246/572) of the isolates were resistant to four or more (multi-resistant). The AmpGenKanTet profile was the most prevalent in carcass isolates and was associated with farm origin.